Global Chlorophyll Concentration Distribution and Effects on Bottom Reflectance of Coral Reefs
2024
Ana G. Bonelli | Paulina Martin | Phillip Noel | Gregory P. Asner
Despite the limited coverage of coral reefs in the world’s oceans, they play a crucial role in global marine biodiversity and providing essential ecosystem services. This study explores the influence of chlorophyll-a (<i>Chl-a</i>) concentration in the water column on the estimation of bottom reflectance (<i>r</i><sub>b</sub>) in coral reefs monitored by the Allen Coral Atlas coral reef monitoring system, using satellite imagery from a Sentinel-2 MSI sensor. We conducted a comprehensive analysis, considering <i>Chl-a</i> global distribution and variability, and its combined effect with water column depth over <i>r</i><sub>b</sub> calculation. Our results demonstrated that the impact of <i>Chl-a</i> on <i>r</i><sub>b</sub> estimation becomes significant when the water column depth exceeds 3 m. While suggesting the optionality of using regional <i>Chl-a</i> values, our study highlights potential overestimations of <i>Chl-a</i> in optically complex environments, such as along the Brazilian coast. This research contributes to refining coral reef monitoring systems and underscores the importance of accurate <i>Chl-a</i> assessments for robust environmental evaluations.
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